JP7057933B2 - Power converter operation control device and operation control method - Google Patents

Description

Embodiments of the present invention relate to an operation control device and an operation control method of a power converter.

In recent years, power generated by a distributed power source using renewable energy such as a photovoltaic power generation system (photovoltaic (PV) system) or a wind power generation system has been used as power supply to private facilities. At this time, the output power of the distributed power source is affected by the influence of the environment such as weather, and stable power supply cannot be expected. Therefore, it is common to use a system power source together.

A power converter (power conditioner (PCS)) is used to convert the DC power output by the distributed power source to AC power, and when the scale becomes relatively large, multiple distributed power sources and corresponding multiple PCSs are used. A system has been devised in which these plurality of PCS and system power supplies are connected in parallel to supply power to the load of private equipment (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-226120

According to the conventional technique, in a system that supplies power to a load using a grid power source, multiple distributed power sources, and a PCS, if the PCS is a type of device that can only perform rated operation, the power is supplied according to the fluctuation of the load. There is a problem that it is not possible to finely control the grain of wood. That is, when the PCS is only rated operation, it is ON or OFF (100% output or 0% output) operation, so that power less than the rating for one PCS cannot be supplied.

In addition, in the case of a type of device having an output suppression function in which the output power is variable from 0 to 100%, the PCS has a characteristic that the response speed is slow, so that sudden load fluctuations and weather fluctuations occur. If the supply is excessive, there is a problem that the power generated by the distributed power source may be supplied to the grid power source, which is a phenomenon called reverse power flow. Reverse power flow causes deterioration of power quality and adversely affects other consumers connected to the same grid power supply, and must be avoided. Further, depending on the model of the PCS, when the reverse power flow occurs, the PCS is forcibly stopped by the interlock function to minimize the state of the reverse power flow. When the PCS is forcibly stopped in this way, a manual return operation is involved, which imposes a heavy burden on the operator.

This embodiment has been proposed to solve the above-mentioned problems of the prior art. An object of the present embodiment is to provide an operation control device and an operation control method of a power converter that follows load fluctuations and avoids reverse power flow.

The operation control device of the power converter of the present embodiment is characterized by having the following configuration.
(1) Multiple power converters that convert the output of a distributed power source that outputs DC power to AC power and output arbitrarily set power.
(2) A system power supply that is connected in parallel with the plurality of power converters and supplies power to the load.
(3) A power value grasping means for individually grasping the output power values of the system power supply and the plurality of power converters.
(4) The electric power supplied to the load is measured by the electric power value grasping means, and one of the plurality of electric power converters is rated and operated so that the electric power supplied from the distributed power source to the load is maximized. The power supplied to the load is divided by the output power of the power converter that has been rated and the value rounded up to the nearest whole number is used as the required number of operating power converters. Control to give the output power value to the remaining operating power converters by dividing the difference between the power supplied to the load and the output power of the one rated operating power converter. means.

The following embodiments are also aspects of the present invention.
(1) When the power value grasping means of the grid power supply grasps the electric power flowing from the load side to the grid power supply side, the control means reduces the number of operating units of the required required power converter by one. Then, one power converter operating other than the rated power converter is stopped .

The embodiment of the present invention also includes aspects of the operation control method of the power converter.

The system block diagram which shows the 1st Embodiment of this invention. The flowchart which shows the number control of PCS of 1st Embodiment of this invention. The flowchart which shows the number control of PCS of 2nd Embodiment of this invention.

(Structure of the first embodiment)
Hereinafter, the configuration of the first embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a system configuration diagram showing a first embodiment of the present invention. In order to supply electric power to the load 1, the supply source is composed of a system power supply 2 and a plurality of distributed power sources 3 connected in parallel to the system power supply 2. The distributed power source 3 uses solar cells 3a to 3e in the present embodiment, but is not limited to this, and may be any device that generates DC power by using renewable energy such as wind power generation. Further, the number of solar cells 3a to 3e is also composed of 5 in this embodiment, but it goes without saying that it is an example.

Power converters 4 (PCS4 (referring to all units), PCS4a to 4e) are connected in a form corresponding to each of the plurality of solar cells 3a to 3e, and the DC power generated by the solar cells 3a to 3e is converted into AC power. It is converted and connected in parallel with the system power supply 2 to supply power to the load 1. Here, the power converter 4 uses a type of device that can be remotely operated / stopped and has an output suppression function in which the output power is variable from 0 to 100%.

A power sensor 5 (power value grasping means) is provided on the output side of the grid power supply 2 and the PCS 4a to 4e to measure the power supplied to the load. Here, although the output power of the PCS4 is detected by the power sensor in the present embodiment, the output voltage may be directly detected from the PCS4 main body as the power value grasping means.

The power value detected by the power sensor 5 is taken into the control device 6 (control means), and the control means 6 calculates the number of operating units for the PCS 4a to 4e and gives an operation / stop command. The control means 6 can be realized by using, for example, a PLC (Programmable Logical Controller), and the signal exchange with the power sensor 5 and the PCS4a to 4e is a DC4 to 20 mA current signal or a serial such as RS-485. Interface etc. can be used.

(Action and effect of the first embodiment)
Next, the number control of the PCS4 of the first embodiment according to the present invention will be described with reference to the flowchart of FIG. The operations and commands shown in the flowchart can be realized by constructing a program in the control means 6, for example. Here, the purpose of controlling the number of PCS 4s is to maximize the power supplied from the solar cells 3a to 3e, which are the distributed power sources 3, to the load 1. That is, the power supplied from the system power supply 2 to the load 1 is minimized.

In step S1 of FIG. 2, the output of the representative PCS is set to 100% (rated operation). As the representative PCS, any one of PCS4a to 4e may be fixed, or which PCS may be switched as the representative PCS at an arbitrary timing. A 100% output command is given to the representative PCS, the generated power is measured by the power sensor 5 (X), and is input to the control means 6. Here, since the power generation source of the generated power is the solar cells 3a to 3e, the generated power is not fixedly determined depending on the weather and the time zone even if the representative PCS is instructed to output 100%. Further, MPPT control (Maximum Power Point Tracking) may be executed in the PCS4 in order to obtain the maximum power generation.

In step S2, the generated power of the PCS other than the representative PCS is measured by the power sensor 5 (Pi) and input to the control means 6.

In step S3, the sum of the electric power generated by the distributed power source 3 is calculated by the formula.
(Y) = (X) + Σ (Pi) ・ ・ ・ (1)
Ask for. Here, (Y) is the total power generation of the distributed power source 3, (X) is the power generation of the representative PCS, (Pi) is the individual power generation of other PCS other than the representative PCS, and Σ (Pi) is. It is the sum of the individual generated power of other PCS.

In step S4, the power (CT) from the system power supply 2 to the load 1 is measured.

In step S5, the power consumed by the load 1 is expressed by the formula.
(A) = (Y) + (CT) ... (2)
Ask for. Here, (A) is the power consumption of the load 1.

Next, in step S6, the operating number (B) of the PCS4 is expressed by the formula.
(B) = (A) / (X) (rounded up to the nearest whole number) ... (3)
Ask for. By dividing the power consumption (A) of the load 1 by the generated power (X) of the representative PCS, the number of PCSs to satisfy the power consumption of the load 1 can be obtained, and one unit is rounded up to the nearest whole number. (To be exact, less than one) We are looking for a large number of PCS. Of course, the number of PCS4s is limited by the number of installations, so if the power consumption of load 1 cannot be covered even if all PCS4s are operated at 100%, the system power supply 2 will supply insufficient power. Become.

In step S7, PCS4 is operated for the number of units obtained in step S6. At this time, if the PCS 4a to 4e to be operated are preferentially operated, for example, from the PCS having the least number of operations, the effect that the number of times the PCS is started is leveled and the life is averaged can be obtained. Further, if the operation time is used as an index instead of the number of operations, the same effect can be obtained. On the contrary, if the operation is performed from the one with the largest number of operations or the one with the longest operation time, the lifespan will come in order, so that it is possible to obtain the effect that the replacement and maintenance due to the lifespan of the PCS can be leveled. Of course, the same applies when the PCS is stopped, and the same effect can be obtained by stopping the PCS from the one with the largest number of operations or the one with the shortest operation time. The number of operations and the operation time of the PCS 4 can be realized by accumulating the count numbers by the control means 6, respectively.

In step S8, the other PCS output setting values are expressed in the formula.
(C) = [(A)-(X)] / [(B) -1] ... (4)
And give the output setting value to other PCS. This is because the numerator “− (X)” and the denominator “-1” exclude the representative PCS component. By doing so, the number of operating PCS4s obtained by the equation (3) was one more, but by giving the output set value (C) to other PCSs in proportion, the power consumption of the load 1 was consumed. It will be possible to supply power equivalent to. In addition, since the PCS is not 100% operated and has a surplus capacity, it has the effect of being able to follow some load fluctuations and power generation fluctuations due to weather changes.

By returning to step S1 and repeatedly executing steps S1 to S8, the number of PCS4s to be operated is determined according to the power consumption of the load 1 and the generated power of the distributed power 3, and the power supplied from the distributed power 3 to the load 1 is the maximum. It is possible to perform control so as to become.

(Second embodiment)
Hereinafter, a second embodiment according to the present invention will be described. Since the configuration is the same as that of the first embodiment, the description thereof will be omitted, and the operation and effect will be described with reference to FIG.

FIG. 3 is a flowchart showing the number control of PCS4 according to the second embodiment of the present invention. In particular, it shows the number control of PCS4 when reverse power flow to the grid power supply 2 occurs, and steps P1 and P2 are added between steps S6 and S7 in FIG. 2, and this difference will be described. do.

The reverse power flow to the grid power supply 2 is detected when the power sensor 5 that measures the power supplied from the grid power supply 2 to the load 1 shows a negative value (step P1).

When the reverse power flow is detected, the operation of reducing the number of PCS4s by one is calculated in step P2, so that the reverse power flow can be eliminated. That is, since the number of operating PCS4s is originally calculated by rounding up the decimal point in step S6, the electric power is reduced by the amount corresponding to the number after the decimal point, and as a result, the reverse power flow is eliminated. Although this can also be realized by the control means 6, since the PLC, which is the realization means, has a very high control cycle, it can be eliminated within 500 msec after the reverse power flow is detected. This has the effect of avoiding deterioration of power quality due to reverse power flow and adverse effects on other consumers connected to the same grid power supply 2.

In step P2, the operation of reducing the number of PCS4s by one is calculated, but the number of PCS4s to be reduced may be increased to more than one according to the magnitude of the reverse power flow.

Depending on the PCS model, the PCS was forcibly stopped by the interlock function when reverse power flow occurred, and in that case, a manual return operation was required and the burden on the operator was heavy. In this case, since it can be handled by a normal stop, the manual return operation of the operator becomes unnecessary, and the burden on the operator can be reduced.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Load 2 ... System power supply 3, 3a to 3e ... Distributed power supply (solar cell)
4, 4a-4e ... Power converter (PCS)
5 ... Power sensor 6 ... Control device

Claims (4)

Multiple power converters that convert the output of a distributed power supply that outputs DC power to AC power and output arbitrarily set power,
A system power supply that is connected in parallel with the plurality of power converters and supplies power to the load,
A power value grasping means for individually grasping the output power values of the system power supply and the plurality of power converters, and
The electric power supplied to the load is measured by the electric power value grasping means, and one of the plurality of electric power converters is rated-operated and supplied to the load so that the electric power supplied from the distributed power source to the load is maximized. The power to be generated is divided by the output power of the power converter that has been rated and the value rounded up to the nearest whole number is used as the required number of power converters to be operated. A control means that divides the difference between the power supplied to the load and the output power of the one rated operating power converter and gives the output power value to the remaining operating power converters. A power converter operation control device. When the power value grasping means of the grid power supply grasps the electric power flowing from the load side to the grid power supply side, the control means reduces the number of operating units of the required required power converter by one, and the said. The operation control device for a power converter according to claim 1, wherein one power converter operating other than the rated power converter is stopped . Multiple power converters that convert the output of a distributed power supply that outputs DC power to AC power and output arbitrarily set power,
A system power supply that is connected in parallel with the plurality of power converters and supplies power to the load,
A power value grasping means for individually grasping the output power values of the system power supply and the plurality of power converters, and
The electric power supplied to the load is measured by the electric power value grasping means, and one of the plurality of electric power converters is rated-operated and supplied to the load so that the electric power supplied from the distributed power source to the load is maximized. Divide by the power to be used and the output power of the rated operated power converter, and the value rounded up to the nearest whole number is used as the required number of power converters to be operated. It has a control step of dividing the difference between the power supplied to the load and the output power of the one rated operating power converter and giving the output power value to the remaining operating power converters. Operation control method for power converters. In the control step, when the power value grasping means of the grid power supply grasps the electric power flowing from the load side to the grid power supply side, the number of operating units of the required required power converter obtained is reduced by one, and the operation is described. The operation control method for a power converter according to claim 3, wherein one power converter operating other than the rated power converter is stopped .

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